Applications of asparaginase enzymes in food technology originate from the finding that a thermal treatment of food converts asparagine in the presence of reducing carbohydrates partly to acrylamide. Since carbohydrates are as ubiquitous as amino acids in food, there is a permanent risk of generating the cancerogenic and genotoxic acrylamide during the thermal treatment of food. The thermal treatment is for example a baking, a roasting, a barbecuing or a deep-fat frying of the food. The onset of acrylamide formation during the thermal treatment of the food is observed at temperatures exceeding 120° C. The Joint FAO/WHO Expert Committee on Food Additives (JECFA) has stated that dietary exposure to acrylamide may indicate a human health concern given its genotoxicity and carcinogenicity.
Particular concerns in the food industry arise for the numerous varieties of for example breads, cookies, snacks, biscuits, cereals, roasted seeds (such as cocoa, coffee), extruded and cut potato products that need to be inherently thermally treated.
The thermal treatment of the food is indispensible for a quality of the food. For example the browning (Maillard) reaction in the food forms the typical flavours, colours, and antioxidants in the food. Furthermore microbial safety and extended shelf-life of the food are achieved due to the thermal treatment of the food.
It would be desirable to enable a selective removal of L-asparagine prior to the thermal treatment of the food.
Genetic engineering of potato using an antisense asparagine synthase gene and tuber specific promoters have been reported to reduce, but not to eliminate asparagine from the potato tuber (Rommens 2007); a full elimination of asparagine is supposedly lethal for the plant.
Enzymes are ideal selective tools to modify a food constituent without affecting other food constituents. A catalytic action of enzymes on the food is distinguished by a high substrate plus reaction specificity and by gentle physical conditions of enzyme action. The enzyme action on the food is more environmentally friendly as no organic solvents or heavy metals are involved (“green chemistry”; “white biotechnology”). Enzymes used to modify the food constituent allow changing a single food constituent whilst avoiding any side-reactions which could eventually result in the formation of toxic compounds in the food.
However, no enzyme technology can be currently envisaged for the selective hydrolysis of a protein bound amino acid, such as asparagine, from a food protein, even less while maintaining the typical structural and sensory properties of the respective food material.
It would be desirable to hydrolyse e.g. free and mobile asparagine in the food to aspartic acid. The asparagine cannot then serve as a precursor molecule for acrylamide formation when the food is thermally treated.